Search results for "wlan"

Revisit of RTS/CTS Exchange in High-Speed IEEE 802.11 Networks

2005

IEEE 802.11 medium access control (MAC), called distributed coordination function (DCF), provides two different access modes, namely, 2-way (basic access) and 4-way (RTS/CTS) handshaking. The 4-way handshaking has been introduced in order to combat the hidden terminal phenomenon. It has been also proved that such a mechanism can be beneficial even in the absence of hidden terminals, because of the collision time reduction. We analyze the effectiveness of the RTS/CTS access mode, in current 802.11b and 802.11a networks. Since the rates employed for control frame transmissions can be much lower than the rate employed for data frames, the assumption on the basis of the 4-way handshaking introd…

Analysis of the IEEE 802.11e EDCA Under Statistical Traffic

2006

Many models have been proposed to analyze the performance of the IEEE 802.11 distributed coordination function (DCF) and the IEEE 802.11e enhanced distributed coordination function (EDCA) under saturation condition. To analyze DCF under statistical traffic, Foh and Zukerman introduce a model that uses Markovian Framework to compute the throughput and delay performance. In this paper, we analyze the protocol service time of EDCA mechanism and introduce a model to analyze EDCA under statistical traffic using Markovian Framework. Using this model, we analyze the throughput and delay performance of EDCA mechanism under statistical traffic.

QoS Mechanisms for IEEE 802.11 Wireless LANs

2004

Currently the Internet provides users with access to information across the world using IP technology. Until now most access points to the Internet have been fixed stations at given locations, but with increasing sales of mobile devices, mobility has become a major trend. Therefore, the Internet is becoming more and more heterogeneous due to the recent explosion of wireless networks. The IEEE 802.11 wireless LAN (WLAN) is the most widely used WLAN standard nowadays. Currently the IEEE 802.11 standard specifies an over-the-air interface between wireless devices. However, QoS services over this technology are still being defined aiming to provide support to multiple applications. Thus, a larg…

An Experimental Testbed and Methodology for Characterizing IEEE 802.11 Network Cards

2006

It has been observed that IEEE 802.11 commercial cards produced by different vendors show a different behavior in terms of perceived throughput or access delay. Performance differences are evident both when the cards contend alone to the channel, and when heterogeneous cards contend together. Since the performance misalignment does not disappear by averaging the environmental factors (such as propagation conditions, laptop models, traffic generators, etc), it is evident that the well known throughput-fairness property of the DCF protocol is not guaranteed in actual networks. In this paper we propose a methodological approach devised to experimentally characterize the IEEE 802.11 commercial …

Nowe stanowisko linderni mułowej Lindernia procumbens na Śląsku Opolskim

2017

Lindernia mułowa Lindernia procumbens (Krocker) Philcox jest rośliną roczną, pojawiającą się w lipcu, kwitnie i owocuje w sierpniu, kończy rozwój późną jesienią wraz z pierwszymi przymrozkami. W Polsce występuje ona bardzo rzadko na rozproszonych stanowiskach, skupionych głównie w dorzeczu górnej i środkowej Odry oraz w dorzeczu górnej Wisły, w miejscach wilgotnych, mulistych lub piaszczystych, na brzegach obu rzek i ich starorzeczy, a także na dnie wysychających stawów hodowlanych, w zbiorowiskach namułkowych z klasy Isoëto-Nanojuncetea. Nowe stanowisko tego gatunku stwierdzono w 2015 roku na dnie wyschniętego stawu hodowlanego w Gąsiorowicach koło Strzelec Opolskich na Śląsku Opolskim

RF fingerprinting for user locationing in LTE/WLAN networks

2016

Location based applications and services have become popular in many wireless communication devices. This thesis study presents a performance evaluation of Radio Frequency (RF) fingerprinting framework in heterogeneous Long Term Evolution (LTE) and Wireless Local Area Networks (WLAN) using Minimization of Drive Testing (MDT) measurements which allow automated construction of extensive RF fingerprint training databases. Utilization of MDT data could create additional opportunities for service provider and application developers. Typical RF fingerprint consist of radio measurements from multiple LTE transceiver stations and WLAN access points. Regardless environmental conditions, received sig…

A CAPWAP Architecture for Automatic Frequency Planning in WLAN

2007

Recently, the impressive success of the IEEE 802.11 WLAN technology has dramatically changed the role of the wireless connectivity provisioning. Born as a wireless extension of small office or home networks, todays the WLANs are getting more and more popular as a large, even metropolitan, area networks. The deployment of large-scale WLANs has some critical issues, because of the lack of coordinated management functionalities among the network nodes. In this paper we briefly describe the CAPWAP architectural solution, for centralizing some control and maintenance functionalities in large scale WLAN, by guaranteeing the interoperability between network nodes provided by different vendors. We …

O utworzeniu Parku Narodowego "Puszcza Śląska"

2016

National Park is in Рolish law one of the most important protection form that is dedicated to areas sustained in natural conditions, having fairly untouched vegetation and biodiversity. Despite that the Silesian Forest-Nature District has a unique areas in terms of nature values as well as cultural and biodiversity heritage, no national parks were established here until now. In the proposed national park of Silesian Forest 50 legally protected plant species were noted, in this 16 listed as threatened in Polish Red Data Book. More than 130 plant species were found rare within the area. Approximately 250 legally protected animal species are found within park borders that are permanent residen…

Performance Optimization in Wireless Local Area Networks

Wireless Local Area Networks (WLAN) are becoming more and more important for providing wireless broadband access. Applications and networking scenarios evolve continuously and in an unpredictable way, attracting the attention of academic institutions, research centers and industry. For designing an e cient WLAN is necessary to carefully plan coverage and to optimize the network design parameters, such as AP locations, channel assignment, power allocation, MAC protocol, routing algorithm, etc... In this thesis we approach performance optimization in WLAN at di erent layer of the OSI model. Our rst approach is at Network layer. Starting from a Hybrid System modeling the ow of tra c in the net…

The search for reference conditions for stream vegetation in northern Europe

2008

Summary 1. The European Water Framework Directive provides a framework for improving the ecological quality of stream ecosystems, with deviation from reference used as a measure of ecological status. 2. Here we examine the possibility of using less impacted stream sites from Latvia, Lithuania and Poland to establish a Danish reference network for macrophyte assemblages, and as a guiding image for identification of possible references sites within Denmark. Both approaches were evaluated using historical Danish records. 3. Four different macrophyte assemblages were identified for mid-sized streams in the Central and Eastern Lowland ecoregions. Macrophyte assemblages could not be delineated us…